Peptide synthesis in room temperature ionic liquids

We demonstrate that chemical peptide coupling using modern coupling agents is efficient in rt ionic liquids. This new approach presents some advantages, especially in the case of hindered amino acids, which are not easy to couple under standard conditions, since high purities for the crude peptides were observed with respect to coupling in classical solvents.     

Olefin self-cross-metathesis catalyzed by the second-generation Grubbs carbene complex in room temperature ionic liquids

Olefin self-cross-metathesis (CM) reactions catalyzed by the second-generation Grubbs carbene complex have been compared in dichloromethane and two kinds of selected room temperature ionic liquids (RTILs). Both the catalyst and the ionic liquids could be simply recovered and reused for at least four cycles just with a little drop in activity. Significant enhancements in the reactivity, yield and reaction rate were achieved.     

Catalytic olefin epoxidation with cyclopentadienyl-molybdenum complexes in room temperature ionic liquids

Complexes of the type (η⁵-C₅R₅)Mo(CO)₃X (X = Me, Cl; R = H, Me), being efficient homogeneous catalysts for the epoxidation of olefins, have been examined for their catalytic performance at 55 °C in systems containing room temperature ionic liquids (RTILs) of composition [BMIM]NTf₂, [BMIM]PF₆, [C₈MIM]PF₆ and [BMIM]BF₄. The catalytic performance for cyclooctene epoxidation depends strongly on the water content of the system, the catalyst solubility in the RTIL, and the reaction behaviour of the RTIL under the applied reaction conditions. The catalysts can be recycled without significant loss of activity when a reaction system containing [BMIM]NTf₂ and [BMIM]PF₆ in a 4:1 relationship is used. High proportions of [BMIM]PF₆ lead to a ring opening reaction (diol formation), due to HF formation and the presence of residual water.     

Wetting study of imidazolium ionic liquids

In this work, we present a systematic contact angles study of a series of 1-alkyl, 3-methyl-imidazolium ionic liquids (ILs) on well-defined polar and nonpolar monolayer surfaces supported on Si wafers. The advancing and receding contact angles of ILs were used to determine the surface energy of the monolayer surfaces using Neumann's equation-of-state and Zisman's critical surface tension approaches. In parallel, the contact angles of conventional probe fluids (molecular liquids) including water, formamide, methylene iodide, ethylene glycol, and hexadecane were determined on the same surfaces. The results obtained showed a great deal of similarity in wetting behavior of ionic vs molecular probe fluids: the contact angles of both sets of liquids followed the same patterns in accord with the surface tension of the fluid. A good agreement was found between the surface energy determined by different sets of liquids.     

Extraction of organic compounds with room temperature ionic liquids

Room temperature ionic liquids are novel solvents with a rather specific blend of physical and solution properties that makes them of interest for applications in separation science. They are good solvents for a wide range of compounds in which they behave as polar solvents. Their physical properties of note that distinguish them from conventional organic solvents are a negligible vapor pressure, high thermal stability, and relatively high viscosity. They can form biphasic systems with water or low polarity organic solvents and gases suitable for use in liquid–liquid and gas–liquid partition systems. An analysis of partition coefficients for varied compounds in these systems allows characterization of solvent selectivity using the solvation parameter model, which together with spectroscopic studies of solvent effects on probe substances, results in a detailed picture of solvent behavior. These studies indicate that the solution properties of ionic liquids are similar to those of polar organic solvents. Practical applications of ionic liquids in sample preparation include extractive distillation, aqueous biphasic systems, liquid–liquid extraction, liquid-phase microextraction, supported liquid membrane extraction, matrix solvents for headspace analysis, and micellar extraction. The specific advantages and limitations of ionic liquids in these studies is discussed with a view to defining future uses and the need not to neglect the identification of new room temperature ionic liquids with physical and solution properties tailored to the needs of specific sample preparation techniques. The defining feature of the special nature of ionic liquids is not their solution or physical properties viewed separately but their unique combinations when taken together compared with traditional organic solvents.     

The electrochemical properties of a platinum electrode in functionalized room temperature imidazolium ionic liquids

The electrochemical behavior of a platinum electrode in a set of 1-alkyl ether (and 1-alkyl)-3-methylimidazolium room-temperature ionic liquids (RTILs) 1–3 ([C_xO_yMim]⁺[Anion]⁻ or [C_xMim]⁺[Anion]⁻, where Mim = 3-methylimidazolium; C_xO_y = 1-alkyl ether; C₇O₃ = -(CH₂)₂O(CH₂)₂O(CH₂)₂OCH₃; C₃O₁ = -(CH₂)₂OCH₃; C_x = 1-alkyl; C₁₀ = C₁₀H₂₁; C₄ = C₄H₉; and ) was studied by cyclic voltammetry and electrical conductivity. This complementary set of imidazolium RTILs allowed us to explore the effect of the imidazolium cation and the counter-ion, both of which affected the electrochemical window of these RTILs. Various electrochemical events with low current values were observed, which diminished the electrochemical windows. Interestingly, RTILs 2b [1-(2-methoxyethyl)-3-methylimidazolium tetrafluoroborate] and 2d [1-butyl-3-methylimidazolium tetrafluoroborate] showed quasireversible charge transfer processes. The length of the functional group attached to the imidazolium cation was shown to be of great influence as larger electrochemical windows, as well as lower electrical conductivities, were obtained with the longer C₇O₃ and C₁₀ functional groups. The largest electrochemical window of 2.0 V was achieved with RTIL 2c, 1-decyl-3-methylimidazolium tetrafluoroborate. Dedicated to the memory of Prof. Francisco Nart.     

Spectroelectrochemical characterization of thin fullerene films in room temperature ionic liquids

Room-temperature ionic liquids were used as electrolytes for in situ studies of the transitions of solution cast fullerene films. 1-Butyl-3-methyl-imidazolium tetrafluoroborate (BMIMBF₄), 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMIMPF₆) and 1-butyl-2,3-dimethylimidazolium tetrafluoroborate (BDiMIMBF₄) were used in this study and the techniques used are cyclic voltammetry and in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Infrared spectra were recorded during the reversible redox processes of the C₆₀ films showing a three-step one electron reduction and reoxidation reaction. After reoxidation some part of the C₆₀ film remained in its form. The IR bands obtained during electrochemical reduction of C₆₀ in ionic liquids were compared with the spectra reported for C₆₀ films upon reduction in the presence of different cations in organic solutions.     

Mesoscopic structural organization in fluorinated room temperature ionic liquids

The presence of fluorous tails in room-temperature ionic liquids imparts new properties to their already rich spectrum of appealing features. The interest towards this class of compounds that are of ionic nature with melting point less than 25 °C is accordingly growing; in particular, compounds bearing relatively long fluorous tails have begun to be considered. In this invited presentation, we show recent results arising from the systematic study of structural properties of a series of fluorinated room temperature ionic liquids, with growing fluorous chain length. At odd with the current understanding of this class of compounds, we show experimentally that they are characterized by the presence of segregated fluorous domains whose size depends on the fluorous chain length. This experimental finding, based on the synergic use of X-ray and neutron scattering, provides a structural scenario at the mesoscopic spatial scale that is in agreement with the recent state of the art molecular dynamic simulations. We speculate on the potential role of this significant compartmentalization of the bulk liquid phase into different nanoscale domains, as relevant in a series of applications including separation, solubility, catalysis, and so forth.     

Catalytic asymmetric hydrogenation of aromatic ketones in room temperature ionic liquids

Polar bisphosphonic acid-derived Ru(BINAP)(DPEN)Cl₂ precatalysts were synthesized and immobilized in room temperature ionic liquids (RTILs) for asymmetric hydrogenation of aromatic ketones with ee values of up to 98.7%. The performance of the Ru catalysts is highly dependent on the nature of imidazolium ILs. For the imidazolium ILs without acidic protons, both ILs and Ru catalysts were recycled by simple extraction and reused. Such a simple immobilization approach also prevented the leaching of Ru (and Ru catalysts) into the chiral secondary alcohol products, and should prove desirable for the production of pharmaceutical intermediates that are free from metal contaminants.     

Synthesis of multi-hydroxyl and sulfonyl dual-functionalized room temperature ionic liquids

Starting from the hydroxylamine (dimethyl amino ethanol, triethanolamine) and 1,3-propane sultone, a series of hydroxyl and sulfonyl dual-functionalized zwitterionic salts and corresponding acidic room temperature ionic liquids have been synthesized. The hydroxyl groups of the synthesized substances were confirmed by the 1H NMR measurement. These zwitterionic salts and ionic liquids may be used for synthesizing other functionalized ionic liquids or ionic liquid-polymer (polyelectrolyte).     

Application of novel room temperature ionic liquids in flexible supercapacitors

This paper studied application of different types of room temperature ionic liquids (RTILs) into flexible supercapacitors. Typical RTILs including 1-buthyl-3-methyl-imidazolium [BMIM][Cl], trioctylmethylammonium bis(trifluoromethylsulfonyl)imide [OMA][TFSI] and triethylsulfonium bis(trifluoromethylsulfonyl)imide ([SET₃][TFSI]) were studied. [SET₃][TFSI] shows the best result as electrolyte in electrochemical double-layer (EDLC) supercapacitors with very high specific capacitance of 244 F/g at room temperature, overceiling the performance of conventional carbonate electrolyte such as dimethyl carbonate (DMC) with more stable performance and much larger electrochemical window.     

室温离子液体催化巯基乙酸异辛酯的合成

巯基乙酸异辛酯是一种广泛应用于精细化工、树脂和塑料制造的中间体,尤其在聚氯乙烯无毒制品中有着重要用途[1],其合成方法的改进也成为研究的主要课题之一。巯基乙酸异辛酯的合成通常采用硫酸催化法[2],由于浓硫酸污染环境、腐蚀设备,特别是近年来环保法规对环境和安全性不断提高的要求,用固体酸(分子筛、离子交换树脂、固体超强酸)等取代H2SO4、HF、A lC l3等强腐蚀性酸作为催化剂的催化工艺获得明显进展[3],但这些催化剂也有自身的缺点[4]。室温离子液体是近年来受到极大关注的一类新材料,它为人们探索环境友好的催化体系和溶剂提供了…     

Olefin metathesis in room temperature ionic liquids using imidazolium-tagged ruthenium complexes

New recyclable imidazolium-tagged ruthenium catalysts have been developed to perform olefin metathesis in room temperature ionic liquids (RTILs). High level of recyclability combined with a high reactivity were obtained in the ring-closing metathesis (RCM) of a variety of di- or tri-substituted and/or oxygen-containing dienes. Extremely low residual ruthenium levels were detected in the RCM products (average of 7.3 ppm per run). Several examples of olefin cross-metathesis (CM) have been also studied.     

Mononuclear rearrangement of heterocycles in ionic liquids catalyzed by copper(II) salts

The reactivity of E- and Z-phenylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole in the presence of CuCl₂ and Cu(ClO₄)₂·6H₂O has been studied in four imidazolium ionic liquids [bmim][X] (X=BF₄⁻, PF₆⁻, SbF₆⁻ and CF₃SO₃⁻). The reaction may follow different mechanistic patterns, depending on the nature of the ionic liquid anion, accounting for both qualitative and kinetic data. In the presence of CuCl₂, two processes take place at the same time, i.e., the E?Z isomerization and the rearrangement of Z-isomer into the relevant 4-benzoylamino-2,5-diphenyl-1,2,3-triazole. In contrast, in the presence of Cu(ClO₄)₂·6H₂O, the rearrangement occurs only in solution of [bmim][BF₄] and [bmim][CF₃SO₃]. Collected data show that the effect of the ionic liquid on the isomerization and the rearrangement is different. In particular, a higher cross-linking degree seems to favour the triazole, but disfavour the E?Z isomerization.     

New ionic liquids with tris(perfluoroalkyl)trifluorophosphate (FAP) anions

The synthesis of new ionic liquids with tris(perfluoroalkyl)trifluorophosphate (FAP) anions is described. The physico-chemical properties (conductivity, viscosity, electrochemical and thermal stability) of this new generation of ionic liquids (molten salts) are discussed. FAP-ionic liquids show an excellent hydrolytic stability, low viscosity and high electrochemical and thermal stability that makes them attractive for use in electrochemical devices and as a new media for application in modern technologies and chemical synthesis.     

Influence of water on the dissolution of cellulose in selected ionic liquids

Cellulose (7% water) was thoroughly dispersed in various ionic liquids (IL) and the turbidity of the mixture was investigated to distinguish real dissolution from fine dispersion. The dissolving ability of 1-butyl-3-methylimidazolium chloride (BMIMCl know cellulose solvent) and 11 other commercial IL (not reported as cellulose solvents) was studied. From the latter, only 1,3-dimethylimidazolium dimethylphosphate (DMIMDMP) could dissolve cellulose. The influence of water content on the real dissolution of cellulose in these two IL was investigated. The maximum theoretical amount of dissolved anhydrous cellulose in the IL was determined by extrapolation methodology at different temperatures. For cellulose in BMIMCl, it was 8.75 g/100 g of IL at 95 °C. DMIMDMP could achieve real cellulose dissolution only in a practically anhydrous system (2.3 g/100 g of IL at 30 °C) but dissolution was physically limited by high viscosity.     

Application of ionic liquids as a catalyst in the synthesis of polyvinyl butyral(PVB) polymer

Polyvinyl butyral(PVB) polymer was successfully synthesized using ionic liquid(IL) catalyst. The synthesis of PVB was achieved by acetalization of polyvinyl alcohol(PVA) and butyraldehyde(BA) in the presence of[HMIM]⁺HSO₄^- IL catalyst. The FT-IR, ¹H NMR, DSC, GPC and SEM characterizations were used to analyze the structure and properties of PVB. The effects of the concentration of PVA in water and the number of reuse cycles on the acetalization degree were investigated. The results indicated that the maximum acetalization degree of PVB obtained using[HMIM]⁺HSO₄^- IL catalyst was up to 72%. The comparison of the commercial PVB and the PVB obtained using[HMIM]⁺HSO₄^- IL catalyst showed that the self-made PVB has a larger molecular weight, higher viscosity, and higher acetalization degree than the commercial PVB.     

The first example of hydrozirconation of alkynes in room temperature ionic liquids

Hydrozirconation of terminal alkynes in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]) at 30 °C gave highly regio- and stereoselectively (E)-vinylzirconium complexes, which underwent a cross-coupling reaction with aryl halides in the presence of Pd(PPh₃)₄ to afford (E)-1,2-disubstituted ethenes in good to high yields. Our system not only avoids the use of easily volatile THF or CH₂Cl₂ as solvent but also solves the basic problem of palladium catalyst reuse.     

Epoxidation in ionic liquids: A comparison of rhenium(VII) and molybdenum(VI) catalysts

Complexes of the type (dimethyl-bpy)MoO₂Cl₂ and Schiff/Lewis-base complexes of methyltrioxorhenium (MTO), being efficient homogeneous catalysts for the epoxidation of olefins, have been examined with respect to their catalytic performance at 55 and 25 °C in systems employing room temperature ionic liquids (RTILs) of composition [BMIM]NTf₂, [BMIM]PF₆, [BMIM]BF₄ and [C₈MIM]PF₆ as solvents. The performance in the cyclooctene epoxidation was observed to be strongly dependent on the water content of the system and the catalyst solubility in the RTIL. MTO based systems prove to be superior with respect to lower energy consumption, higher stability and higher product yields compared to the investigated Mo(VI) system under the conditions applied.     

室温离子液体在分离科学研究中的新进展

室温离子液体作为一种重要的绿色溶剂,由于在金属离子、小分子有机物的萃取分离,气体吸附分离以及作为液相和气相色谱固定相等许多分离过程中体现出高分离效率和高选择性的特点,正在成为分离科学研究的前沿领域.着重总结了从2003—2006年的室温离子液体在分离科学领域中的新进展,并对其应用领域和发展前景做了展望.提出进一步加强离子液体的功能化和固定化技术及其在分离科学中的应用基础研究,探索离子液体有效的回收和再循环利用的新方法,是离子液体今后在分离科学研究中的一系列重要内容.